The present invention relates to capacitors, and, more particularly, to multiple capacitors for use in conjunction with printed circuit boards and the like.
The introduction and development of integrated circuit technology has created the capacity to fabricate an extraordinarily large number of active electronic elements on a single circuit die. Such circuits provide functionality to a depth and extent that appeared to be fantastic only a few years ago. One result of these developments has been the miniaturization of electronic devices that were formerly large and bulky, by using integrated circuit packages mounted on printed circuit boards with the necessary ancillary devices.
Many electronic devices require some reactive elements to carry out their designed functions. Due to the fact that inductors are generally larger and noisier that capacitors, circuit board designers have tended to eliminate inductors in favor of capacitors to provide the required reactance. Capacitors have also been miniaturized as much as possible to reduce the area they occupy on a printed circuit board. Capacitors are typically provided as discrete components that are mounted on a circuit board by soldering or other techniques known in the prior art. However, there are physical limitations that constrain the miniaturization process, such as the need for high breakdown voltage, which demands a minimal thickness of a high dielectric material Likewise, the capacitive effect is based on separated charge planes, and there are limits to the ways in which the charged conductors can be folded or compacted into a small package. As a result of these limitations, a single capacitor on a circuit board may occupy a substantial fraction of the area required for an integrated circuit package that may contain thousands of active elements. Recognizing that circuit board area is related directly to the cost of the board, there is an ongoing need to further reduce the size of capacitors to the greatest extent, while still providing the requisite capacitive value and operating voltage.
In U.S. Pat. No. 5,500,895, issued to Gerald Yurgelites, there is described a method and apparatus for transmitting communications signals across an electrical isolation barrier. One example of this invention is the transmission of telecommunications signals across the isolation barrier that is required between a telephone network and any telephonic device (telephone, facsimile machine, modem, and the like). This invention employs paired capacitors connected across the isolation barrier, and differentially charges the paired capacitors to deliver the signal across the barrier without breaching the isolation that the barrier provides. Although the electronic circuits required for this purpose have been rendered in integrated circuits that require very little circuit board area, it has been found that the capacitors of the invention require a substantial fraction of the area of the integrated circuits. It would be advantageous to reduce the area that these capacitors occupy. Likewise, there are many other situations in which further miniaturization of capacitors mounted on a circuit board would be beneficial.
Further, there are many electronic circuits that require capacitors that are paired and matched in capacitive value for proper signal handling and the like. Obtaining matched pairs of capacitors typically involves an additional cost above and beyond the cost involved in obtaining two capacitors that are within a common specification but not closely matched. It would be desirable to be able to obtain matched capacitors without having to pay a premium price.